import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();
        char[] arr=str.toCharArray();
        for(char x:arr){
            if(!hs.contains(x)){
                hs.add(x);
            }
        }
        for (char c:hs) {
            System.out.print(c);
        }
    }
}